ISOLATION AND CHARACTERIZATION OF AN ANTICOAGULANT PRESENT IN THE SALIVARY-GLANDS OF THE BONT-LEGGED TICK, HYALOMMA-TRUNCATUM

A low molecular mass anticoagulant (17 kDa) was isolated from the sali vary glands of prefed female Hyalomma truncatum ticks by means of reve rse phase and anion-exchange HPLC. Trypsin digestion and amino acid an alysis confirmed the protein nature of the anticoagulant. The inhibito r appears to be uncompetitive with a K-i of 6.9 x 10(-10)M. The target of the anticoagulant is factor Xa at the junction of the extrinsic an d intrinsic pathways. This may be crucial for the survival of the tick , making it feasible to investigate the possibility of vaccination wit h this antihaemostatic against tick feeding. In addition, tick anticoa gulants may possibly have therapeutic application in controlling throm bosis.